1. Field of the Invention
The present invention relates to a paper feed apparatus of a copier, etc. that separates and sends out one sheet at a time from a bundle of sheets such as originals or recording paper, and more particularly, to a paper feed apparatus having a paper edge regulation mechanism that evens up the edges of sheets.
2. Description of the Related Art
Conventionally, a paper feed apparatus provided for a copier, etc. is equipped with a paper edge regulation mechanism that evens up the edges of sheets to prevent double-sheet feeding or oblique feeding, during feeding of sheets of paper placed.
A conventional paper edge regulation mechanism evens up the edges of sheets placed by moving up and down a paper edge regulation element for evening up the edges of sheets using a solenoid. When paper is placed, this paper edge regulation mechanism lifts the paper edge regulation element, makes the edges of sheets contact the paper edge regulation element and evens up the edges of sheets. On the other hand, when paper is fed, this paper edge regulation mechanism lowers the paper edge regulation element, makes the paper edge regulation element detach from the edges of sheets and at the same time lowers a pickup roller, makes it contact the upper surface of paper, rotates the pickup roller and sends out paper to a feeding roller.
However, the paper edge regulation mechanism above has an ascending/descending mechanism that moves up and down the paper edge regulation element and an ascending/descending mechanism that moves up and down the pickup roller as independent mechanisms, which produces a problem of having a complicated apparatus configuration. Moreover, it is necessary to secure a space for installing these complicated mechanisms in the apparatus, which is an obstacle to miniaturization of the apparatus. Furthermore, it is also necessary to synchronize the ascending/descending timing of the paper edge regulation mechanism with the ascending/descending timing of the pickup roller. However, the paper edge regulation mechanism and pickup roller are operated by the two different ascending/descending mechanisms. For this reason, it is necessary to accurately control the timing and this adjustment is complicated.
Therefore, a technique of mechanically linking the timing at which the paper edge regulation element contacts the edges of sheets with the ascending/descending timing of the pickup roller is proposed. The Utility Model Publication No.HEI 2-57846 discloses a paper feed apparatus, which mechanically links the timing at which the paper edge regulation element contacts the edges of sheets with the ascending/descending timing of the pickup roller.
FIG. 16A and 16B show a configuration of the paper feed apparatus described in the above Publication. Paper edge positioning element 3 is attached to rotation axis 5 of pickup roller 4 in a pivotable manner. This makes paper edge positioning element 3 ascend or descend in synchronization with the ascent or descent of pickup roller 4. Moreover, first protrusion 3a and second protrusion 3b are formed on paper edge positioning element 3 extending in different directions. When pickup roller 4 is in a position above paper 2, first protrusion 3a evens up the edges of sheets 2 and second protrusion 3b touches stopper 6. In this state, even if paper 2 presses first protrusion 3a, second protrusion 3b touches stopper 6 and the rotation of paper edge positioning element 3 itself is regulated. In this way, first protrusion 3a remains stationary with the edges of sheets contacting and acts so as to even up the edges of sheets. On the other hand, when pickup roller 4 descends until pickup roller 4 touches paper 2, second protrusion 3b separates from stopper 6, first protrusion 3a is pressed by paper 2 and paper edge positioning element 3 itself rotates. As a result, first protrusion 3a moves up to a position where first protrusion 3a does not block feeding of paper 2.
The feeding apparatus above eliminates the need to move up or down the paper edge regulation element using independent mechanisms, making it possible to save space. Moreover, paper edge positioning element 3 ascends or descends, while being held in a pivotable manner to the rotation axis of pickup roller 4. This ensures synchronization between the ascending/descending timing of paper edge positioning element 3 and the ascending/descending timing of pickup roller 4.
However, the above paper feed apparatus described in the Publication has the following problem:
That is, in the above paper feed apparatus, when pickup roller 4 ascends, paper edge positioning element 3 also ascends and second protrusion 3b touches stopper 6. As a result, even if paper 2 pushes first protrusion 3a, the rotation of paper edge positioning element 3 is regulated. In this case, when paper 2 is strongly pressed to first protrusion 3, the rotation of paper edge positioning element 3 itself is regulated by contact between second protrusion 3b and stopper 6. Thus, second protrusion 3b is strongly pressed to stopper 6. In this case, as the pressing force to this second protrusion 3b increases, frictional force between second protrusion 3b and stopper 6 also increases. When pickup roller 4 is lowered in this state, the above frictional force prevents pickup roller 4 from descending smoothly, causing aproblemof blocking paper feeding. Especially, when the location where second protrusion 3b touches stopper 6 is above the horizontal position of pivot 5 of pickup roller 4, the track of second protrusion 3b moves in the direction in which stopper 6 is pushed. This causes second protrusion 3b to be further pushed to stopper 6.